The Finnish newspaper Helsingin Sanomatreported that eight people had been taken to the hospital following the stabbings, some of whom were in critical condition.

Translated from Finnish, he wrote: "The Government will closely monitor the situation and the ongoing police operation in Turku".

Security was tightened throughout the country after the stabbing and National Police Commissioner Seppo Kolehmainen warned armed security personnel may be seen in the streets.

The incident is not treated as a terror attack at this stage, police spokesman said, adding they would not confirm if the perpetrator yelled something in Arabic. The attacker shouted extremist slogans allegedly linking him to the Daesh Takfiri terrorists, they said.

The attacker, who was shot in the leg by police and taken into custody, was an 18-year-old Moroccan. "People are requested to avoid the city centre".

Police have so far only described him as "a young man of foreign origin", providing no other details except to say they were collaborating with the Finnish Immigration Service.

Several persons stabbed in central Turku. We saw a man on the square and a knife glittered. "I understood that he had stabbed someone", Laine was quoted as saying. They also issued a warning to people to stay alert at public places, especially train stations and airports.

Turku, with a population of around 180,000, is located on the southwest coast of Finland, 90 miles west of Helsinki.

On Thursday, a suspected Islamist militant drove a van into crowds in Barcelona, Spain, killing 13 people and wounding scores of others.